A bis(trimethoxysilylpropyl) disulfide, bis(triethoxysilylpropyl) disulfide, bis(trimethoxysilylpropyl) tetrasulfide, bis(triethoxysilylpropyl) tetrasulfide, or similar bis(trialkoxysilylalkyl) polysulfide and a method of manufacturing of the aforementioned polysulfides are well known in the art (see Patent References 1 and 2: Japanese Patent Application Publication [hereinafter referred to as Kokai] S48-29726, i.e., JP48-29726A and Kokai S50-108225, i.e., JP50-108225A respectively). A bis(trialkoxysilylalkyl) polysulfide is also well known as a component of rubber compositions that contains a carbon black and a silica filler (see Patent Reference 3: Kokai H08-259734, i.e., JP08-259734A; Patent Reference 4: Kokai H09-227722, i.e., JP09-227722A; and Patent Reference 5: Kokai 2001-31798, i.e., JP2001-31798A).
Also known in the art are sulfur-cured rubber compositions for manufacture of industrial rubber products and rubber tires that have to possess high strength and wear resistance; such compositions contain a silane-coupling agent, carbon black, precipitated silica, fumed silica, or similar fillers with reinforcement properties (see Patent Reference 5 [see above] and Patent Reference 6: Kokai: 2004-196937, i.e., JP2004-196937A).
At the present time a demand in the field of rubber compositions used for the manufacture of air-filled automobile tires, and especially of tire tread, is for development of new technique that could improve engagement of the tire grooves with a wet road (wet-skid resistant properties) and fuel-consumption characteristics of the tires. It has been found that when a tire is manufactured from a rubber composition such as a silica-filled rubber composition with silicone.vinyl type polymer composite rubbery particles, then the vulcanized rubber obtained from this composition has an increased value of tan δ at 0° C., and a reduced value of tan δ at 60° C. Based on this observation, a tire rubber composition and, in particular, a tire-tread rubber composition that has a balance between the wet-skid resistant properties and fuel-consumption characteristics was proposed (see Patent Reference 6).
On the other hand, Patent Reference 7 (US2006/036034A1; WO2006/019963A1) discloses a bis(cyclic alkoxysilylalkyl) polysulfide prepared by causing a reaction between a bis(trialkoxysilylalkyl) polysulfide and an alkanediol. The above reference also discloses a rubber composition for tires based on the use of the aforementioned bis(cyclic alkoxysilylalkyl)polysulfide.
However, when in the processes of the aforementioned Patent References 3, 4, 5, and 6, a bis(trimethoxysilylpropyl) disulfide, bis(triethoxysilylpropyl) disulfide, bis(trimethoxysilylpropyl) tetrasulfide, bis(triethoxysilylpropyl) tetrasulfide, or a similar bis(trialkoxysilylalkyl) polysulfide is mixed with a silica filler and an organic rubber, such mixing causes hydrolysis of the alkoxysilyl groups which is accompanied by generation of low-boiling-point alcohols such as methyl alcohol and ethyl alcohol. Therefore, the technique proposed in the above patent applications causes environmental problems in connection with the preparation of the rubber composition and manufacturing of the vulcanized rubber.
In the invention of Patent Reference 7, mixing of a bis(cyclic alkoxysilylalkyl) polysulfide with a silica filler and an uncured organic rubber generates, due to hydrolysis of the cyclic alkoxysilyl groups, an alkanediol that does not have a sufficiently high boiling points. Therefore, environmental problems associated with the production of the rubber compound and the vulcanized rubber remain unsolved.